Commonly assigned U.S. Pat. Nos. 4,418,828 and 4,497,765 disclose a tamper-indicating plastic closure construction which has proven to be highly commercially successful in light of the efficiency with which it can be formed, and the consistent and reliable tamper-indicating characteristics which it exhibits. The latter of the above patents discloses a method of making the closure with highly desirable efficiency and consistency.
In particular, the construction includes an annular pilfer band which depends from a skirt portion of a plastic closure cap. The pilfer band includes a plurality of circumferentially spaced, inwardly extending flexible projections which are configured to coact and cooperate with an annular locking ring portion of an associated container. The pilfer band is generally distinguished from the closure skirt portion by a horizontal, circumferentially extending score, and is at least partially detachably connected to the skirt portion by frangible means preferably comprising a plurality of circumferentially spaced frangible ribs. Attendant to removal of the closure from a container, the flexible projections coact with the locking ring to fracture the frangible ribs, thereby providing plainly visibly discernable evidence that the closure has been partially or completely removed.
In one embodiment of the above-described closure, a connector portion is provided between spaced apart ends of the horizontal score formed between the pilfer band and skirt portion. The connector portion integrally connects the pilfer band to the skirt portion after fracture of the frangible ribs, whereby the pilfer band remains connected to the closure cap after removal from the container.
In this arrangement, the pilfer band is preferably provided with at least one fracturable area which fractures attendant to closure removal. This fracturable area can comprise one or more scores or cuts formed in the pilfer band generally adjacent to the connector portion which joins the band to the skirt. After removal from the container, the fractured pilfer band typically takes on a curl-like configuration; as a consequence, this type of closure is sometimes referred to as having a pilfer band which forms a "pigtail".
In order to promote convenient removal of closures of the above type from containers, it is desirable that the pilfer band be configured to fracture without undue application of force thereto. On balance, it is important that premature failure of the pilfer band be avoided so that it reliably indicates closure removal.
As noted, one or more scores can be formed in the closure pilfer band in order to form a fracturable area. More specifically, a vertically extending score can be formed so that a non-scored, residual portion of the pilfer band is defined, which said residual portion fails and fractures attendant to closure removal. While it would appear that a readily fracturable construction can be formed by merely scoring the closure pilfer band to define a sufficiently small residual portion, experience has shown that formation of a residual portion which is sufficiently small as to be easily fractured during closure removal is frequently prone to premature failure during formation of the residual portion itself. In this regard, it has been determined that the cutting edge or edges of the one or more blades employed for forming the fracturable residual portion exert a wedge-like action on the pilfer band during scoring which can result in failure of the residual portion as it is formed. Naturally, this is undesirable since the pilfer band must be intact for use as intended.
Further, experience has shown that in some instances, the one or more vertical scores formed in the pilfer band can undesirably propagate, and result in formation of a crack in the plastic material of the closure. Such score propagation can particularly be a problem, attendant to high-speed manufacture, when the pilfer band is scored to provide its fracturable area before the closure is scored horizontally to distinguish the pilfer band and skirt portion.
In order to abate propagation of the vertical score(s), efforts have been made to first score the closure horizontally, and thereafter effect vertical scoring. However, such efforts have met with limited success, since the vertical scoring can undesirably fracture one or more of the frangible bridges which are formed attendant to the horizontal scoring.
Accordingly, it is desirable to provide a closure pilfer band construction which avoids premature band failure, and which avoids crack formation or the like, while promoting formation of a closure which can be easily and conveniently removed by consumers.